let's bring in our pentagon correspondent, chris lawrence. he's joining us on the very sophisticated operation that freed that little boy and what similar operations could look like in years ahead. chris, what are you seeing? >> reporter: yeah, wolf. we're now learning that the fbi used drones likely provided from the u.s. military to keep around the clock surveillance on that particular bunker. that coming from former fbi official tom fuentes who has been talking to his sources. the future and what the fbi may be able to do down the line goes way beyond what was done here. >> reporter: a little boy barricaded in a bunker with a killer. as the crisis stretched into a seventh day, an fbi hostage rescue team practiced how to save him. law enforcement sources now say the fbi built a mockup of the bunker and trained on how they'd go in. but how would they know what was happening below? a law enforcement source tells cnn authorities managed to slip a camera into the hideout. >> we're going to try to introduce microphones and fiber optic lenses int